Inflatable diaphragm for hydraulic presses



Sept. 11, 1956 c. A. LAMB 2,762,395

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am mm Mmm f f mm. mw .ww 9N @n Nm ,//MM//MN\ www mm NN N MN .a N Nm a @www INVENTOR. CHAR/.E5 Af LFI/V15 United States Patent O INFLATABLE DIAPHRAGM FOR HYDRAULIC PRESSES Charles A. Lamb, Glendale, Calif., assigner to Lamb Rubber Corporation, Glendale, Calif., a corporation of California Application August 20, 1953, Serial No. 375,547

4 Claims. (C1. 137-791) This invention relates to hydraulic presses employing inatable bags for transmitting hydraulic pressure to the work to be formed in the press.

This invention relates particularly to the form of hydraulic presses using inflatable bags employing elastomeric spacers such as rubber to transmit the hydraulic pressure from the bag to the work. Such types of presses are known in the trade as Hydro-form presses, the term arising from the fact that the rubber medium under pressure acts as a plastic solid which on deformation transmits the pressure to the work to be formed.

A particular feature of this invention and an object thereof is to construct the inflatable bag so that it will have a satisfactory cycle life; in other words, so that the bag may be operated under very high pressure up to 5,000 or more pounds per square inch and inflated and dellated in its working operations a great number of times without failure.

The usual tiuid for generating the pressure to the inilated bag is oil. It is, therefore, desirable to use the oil resistant elastomers formed of neoprene, which is one of the best known of such rubbers. Neoprene is a trade narne of a polymer manufactured by the E. I. du Pont de Nemours Company and is a chloroprene polymer. Other types of bag material which will stretch under pressure may be used where other fluids are employed as a pressure generating medium. Thus rubber may be employed in the construction of the bag if water is employed as the pressurizing medium.

Such elastomers, in order to function properly as bags, must have suitable elasticity and therefore cannot be vulcanized or hard, but must be flexible. Such bags when employed in hydraulic bags, on deflation and ination, rub against the sides of the press compartment in which they are contained and tend to become weakened and tear or break and thus have a shortened lifetime. This is particularly true where there are sharp corners or edges, and also it is particularly true at the surfaces of the bag which Contact the walls of the press compartment.

In the bag construction of my invention, I form the bag so that one side of the bag is formed of a, relatively rigid member and form the other side of the bag of a flexible membrane which is connected to the rigid member adjacent the edges of the rigid member to form a hollow bag. The membrane in its unstretched condition lies against, i. e., abuts, one side of the rigid member in non-adherent contact. When pressure is introduced between the rigid member and the flexible membrane it will cause the flexible membrane to become stretched but the rigid member is not distorted. The rigid member thus acts as a rigid structural supporting member to support the bag in the desired position in the press compartment.

The bag may thus be made large and be held in position in the press compartment in a manner to be described more fully below.

These and other objects of my invention will be more fully described in reference to the drawings, in which:

Fig. 1 is a vertical section of the press showing the bag in deliated position and prior to the application of the forming pressure, and showing the parts somewhat schematically;

Fig. 2 is a section similar to Fig. l showing the bag in inflated position and the work having been formed around the form block;

Fig. 3 is a section taken on the line 3-3 of Fig. 2;

Fig. 4 is a section taken on the line 4 4 of Fig. 2;

Fig. 5 is a plan view of the bag;

Fig. 6 is a View taken on the line 6-6 of Fig. 5;

Fig. 7 is a section taken on line 7-7 of Fig. 5;

Fig. 8 is a detail showing the edge construction of the bag of Fig. 6 and showing also the position of the bag section when pressure is introduced into the bag; and

Fig. 9 is an elevational view of Fig. 5.

The press 1 may have a vertical section which is ellipsoidal or circular or other shape, illustrated in Fig. l, or any other horizontal sectional shape such as rectangular. The press has a circumambient wall having a top 2, sides 3 and 4, and bottom 5, thus forming a press chamber 1. The chamber 1' is thus milled out in rectangular form as shown and extends between the ends 6 and 7 of the press chamber 1'. The ends are closed by end plates 8 and 9 Which t tightly against ends 6 and 7 and are held in place by tie bolts 10, 11, 12, and 13 passing through suitable longitudinal bores in the press 1.

The end plates extend part way over the end openings 14 and 15, thus forming entrance ports 16 and 17 underneath the end plates 8 and 9 for purposes to be more fully described below.

The press l is drilled with a bore 18 for purposes to be described more fully below.

Positioned in chamber 1 is a bag 19 whose construction is shown in more detail in Figs. 5 to 8. The bag 19 is formed of a plate 20 which conforms with the horizontal section of the press chamber 1. In the case of the rectangular press chamber 1 the plate 20 is of the rectangular shape illustrated in the drawings. The plate has a central boss 21 illustrated as rectangular but which may be of any desired shape. The peripheral rectangular edges of the plate 20 are formed with a bead 22 which extends around the periphery of the plate. The bead extends above the surface 23 of the plate thus forming, with the boss 21, a rectangular depression in the exterior surface of the plate 20 between the wall of the boss 21 and the Wall 22' of the bead 22. Centrally disposed of the plate 21 is a bore 24 and a counterbore 25 in which is set a fitting 26 suitably positioned as by Welding shown at 27 and into which is secured a pipe fitting 28.

The elastomeric membrane forming the inflatable bag is molded in position as shown in Fig. 6 by the following procedure.

The peripheral edges of the elastic membrane are cemented in the depression 23 from a point adjacent the peripheral corner 29 of the depression 23 where the base of the depression 23 intersects the peripheral interior wall 22' of the bead 22, and is also cemented along the base of the depression 23 and along the vertical edge of the boss 21. The bag 31 is thus free and not cemented to the plate from the point 29 over the curve of the bead 22, and is free and not in adhering contact with the interior surface 30 of the plate 21. When cemented in place and with atmospheric pressure on both sides of the membrane 31 the membrane in unstretched condition contacts the surface 30.

The membrane 31 is formed as One integral molded product extending across the interior surface 30 over the bead 22 and into the depression 23, where it is cemented to the surface of the plate 21. The metallic surface from the point 29 over the bead 22 and over the surface 30 is untreated; in other words, the metal surface is not treated, as is well known uncured rubber will not adhere to untreated metal surfaces. The surface of 23 and the vertical surface 23 are treated for adherence or bonding of the neoprene.

Methods of bonding neoprene or rubber to metal are well known and need not be described in detail here. For example, one well known method and one that I have used successfully consists in Sandblasting the surfaces 23 and 23'; for example, by cleaning the surfaces with toluene and then Sandblasting and coating with rubber cement, such as is conventionally used in the rubber trade for adherence of metal surfaces to rubber. Uncured rubber sheet is placed around the plate so that the edges of the sheet extend over the beads 23 and fit into the depressions 23.

A cylindrical core plug is inserted through 34 and projected a short distance; for example, to lin" below the end of 2S. The end of the plug may be formed of a somewhat flexible, cured rubber plug which conforms with the ared mouth of the fitting 25.

When the sheet is cured the rubber plug will not adhere to the rubber sheet and may be withdrawn, leaving a central depression 32' in the sheet 32.

Prior to setting the plate in the curing mold, where the bag is to be used in the form of press illustrated in Figs. l, 3, 9, and l0, I set guard channels 33, which fit along the parallel edges of the plate 20 and over the sheet to be molded, over the bead.

The rubber is then molded around the plate in a suitable manner und cured under pressure in a suitable mold. The cured rubber sheet will adhere to 23 and 23 but will not adhere to 22 and 30. It will also be observed that the plate 21 acts as a core plate 20 which permits the molding of the rubber sheet into one integral sheet construction cemented to the plate 20 and yet will permit the bottom 32 to act as an inflatable membrane since it is free from the core plate 20. lt will be observed that the guard channels 33 embrace the acute bend of the membrane over the periphery of the plate 20.

With the end plates removed the bag is slid into the chamber 1 and placed in position with the pipe 34 fitting into the bore 18 and connected to the fitting 2S.

lt will be observed that the rigid plate 20 which extends across substantially the entire surface of the membrane 32 is held against the wall 2 by the fitting 26 and the pipe 34. This then holds the edges of the membrane 32 against the top 2. ln bags of large area, for example, where the membrane surface 32 is of the order of 1000 square inches, the weight of the membrane 32 is suliicient to cause it to sag downward into the chamber 2 sulliciently to interfere with the insertion of the carriage 43. En order to prevent this a suction is created via 34, as will be more fully described below, and this holds the membrane against the plate 20. ln order to facilitate the exhaustion of air, I provide the depression 32 `which is as shown in Fig. 6 at least as large as the mouth 24. In its absence the rubber surface underneath the mouth of 24 would act as a butterliy valve and shut off before the entire bag is evacuated.

With the top surface of the boss 21 against the top 2 of the chamber l, the metallic spacer blocks 35 are positioned carrying the rubber form pad receiving grooves 36. The rubber pad 37 is positioned in the grooves and extends the full length of the chamber 1 between the walls 4 and 3. The metallic spacer blocks 38 formed to conform with the abutting edges of the membrane 32 formed over the bead, are then fitted in to till in the space between the edges 39 of the bag 31 and over the top of the walls 3 and 4. The spacer blocks 38 carry the containing grooves 40 to receive the pad 37.

The forming block, which may be of any form desired or be any die shape desired, shown at 41, is positioned on a slidable carriage tray 42 having a base 43 and four side walls 44, which malte a slidable fit with the vertical surfaces of the blocks 35. The work, for example, is

shown positioned at 45 and rubber fillers are placed at 46 and an additional rubber pad placed at 47 to fill in around the work and between the work and the pad 37.

When hydraulic pressure is exerted through 34 from any source desired, the membrane 32 is stretched away from the metallic plate from a point shown at 29 around the base of the bead 22 and away from the surface 30, the membrane stretching sufficiently to distort and cause the rubber 37, 47, and 46 to flow and create a forming pressure on the work 45 to conform it to the form block or die 4l.

lt will be observed that this pressure also hold the plate 26 against top 2 and acts, by making the boss 19 of proper height over the bottom of the depression 23, to clamp the membrane 32 in the depression 23 between the top Z and the plate 20 to prevent any tearing away of the rubber from the plate 20 at its cement bond.

When the work has been formed about the form block the hydraulic pressure is released and the fluid is with` drawn creating a vacuum inside the bag, causing the inflatable membrane 32 to contact the bead 22 and the surface 30 snugly, as has been described above. This releases the pressure on the forming rubber material and it regains its position and the bag is held by suction, and the carriage 43 may be withdrawn. The carriage 43 is withdrawn underneath one of the end plates 15 or 16 carrying with it the form work and the rubber fillers 46 and 47.

As described above, plate 20 holds the inflatable bag against the top 2. This prevents the bag from sagging and supports the top of the bag rigidly. If the bag had been made completely fiexible so that the top is exible as well as the bottom, the whole bag, being of sufiicient weight, would then sag and distort the forming pad 47 so as to interfere with the reinsertion of the carriage 43.

l therefore obtain from the plate 21 a plurality of functions: first, it is a core for forming an integral membrane and therefore I do not have to rely upon a bag formed by cementing two membranes at their edges. The plate also acts as a separating core in molding the bag so as to form the sheet over the edges of the plate. The plate also acts as a rigidifying member to permit the bag to be held in place at the press.

While I have described a particular embodiment of my invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

I claim:

l. An inflatable bag for hydraulic presses comprising a rigid plate having a peripheral edge and two sides, an opening in said plate extending through said plate, n first of said sides having an upstanding peripheral bead around said peripheral edge and being formed with a depression relative to the top of said bead located inwardly of said bead and extending generally parallel and adjacent thereto, a flexible and extensible membrane positioned over a second of said sides of said plate and extending integrally across said second side and over said opening, said membrane also extending over the peripheral edge and over a portion of said first side of said plate inwardly of said bead and fitting into said depression, said membrane being in nonadherent con tact with and free of said second side and said peripheral edge of said plate, a cement bond between said membrane and said first side of said plate in said depression, whereby fiuid pressure introduced through said opening causes said membrane to be inliated and to be extended away from said second side of said plate and said peripheral edge.

2. A bag as defined in claim l, wherein said membrane forms an acute bend about said peripheral edge, and further including a guard channel mounted exteriorly of and extending over said membrane at said peripheral edge and embracing said acute bend of said membrane.

3. A bag as defined in claim 1. wherein said membrane is provided with a depression in the side thereof facing said second side of said plate and located opposite said opening through said plate, said depression in said membrane being at least of substantially the same size as said opening through said plate.

4. A bag as defined in claim 1, wherein said membrane forms an acute bend about said peripheral edge, and further including a guard channel mounted exteriorly of and extending over said membrane at said peripheral edge and embracing said acute bend of said membrane, and wherein said membrane is provided with a depression in the side thereof facing said second Side of said plate and located opposite said opening through said plate, said depression in said membrane being at least of substantially the same size as Said opening through said plate.

References Cited in the tile of this patent UNITED STATES PATENTS Tatter Aug. 29, Brisson Feb. l, Sauzedde Oct. 29, Hastings Nov. 12, Walton May 8, Breit Nov. 28, Thorburn et al Aug. 26, Dale Dec. 8, Fawick Mar. 30, 

